Asymmetric Biocatalytic Reduction of Cyclic Imines: Design and Application of a Tailor-Made Whole-Cell Catalyst

Abstract

The design of a recombinant whole-cell catalyst and its utilization in the asymmetric reduction of 1-methyl-3,4-dihydroisoquinoline chosen as a model substrate for cyclic imines is presented. As "designer cells" E. coli cells bearing the two enzymes imine reductase and glucose dehydrogenase (for in situ-cofactor recycling) were constructed, which turned out to be suitable for the asymmetric reduction of 1-methyl-3,4-dihydroisoquinoline at low biocatalyst loading of 2 g/L up to 10 g/L of lyophilized cells, leading to both high conversion and enantioselectivity of >99% ee of the resulting amine. The stoichiometric reducing agent is readily available D-glucose, and a proof of concept for running the reactions at elevated substrate concentration of up to 100 mM was demonstrated.